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Tuberculosis guidelines
Further, the similarities in TB disease trends between
Australia and countries where universal BCG vaccination
has never been practised (USA, Netherlands)
suggest that the incidence of TB in a community is
determined by the combined effect of all TB control
measures rather than BCG vaccination alone.
BCG vaccination does not prevent the transmission
of infection to an individual. Its direct effect for which
it was introduced appears to be in limiting the spread
of primary infection in an infected individual. Varying
reports suggest levels of protection anywhere from
0 to 80 per cent. 4,5,6,7 The differences possibly relate
to use of different BCG strains, methodological factors,
the infl uence of environmental mycobacteria
and age, immune or genetic factors. 8
Recent meta-analyses have been helpful in summarising
the variable fi ndings from several studies
on BCG effi cacy. The key conclusions were that it
is about 50 per cent effective in preventing disease
and that the most important protective benefi ts are
in minimising the risk of death, meningitis and miliary
disease in neonates and young children. 9,10
Although the use of BCG in health workers has
waned considerably there has been renewed interest
related to multi-drug resistant TB. 7 The benefi t
of BCG vaccination over TST screening may be
enhanced for the health worker in such a setting. 11,12,13
It offers some protection irrespective of drug susceptibility
status, whereas the benefi t of preventive
therapy is unproven in those infected with an MDR
strain. 14,15 This dilemma highlights the importance
of appropriate infection control measures in health
care settings.
Risk groups
For the majority of Australian born now, the risk of
acquiring TB infection and developing disease is
very low. However certain groups in our community
are considered at increased risk. 16–18
The National Health and Medical Research Council
(NHMRC) consensus statement has defi ned high
risk as referring to those subgroups of the population
who have an annual notifi cation rate above
25 cases per 100,000 population. 19 This provides
a useful criterion for determining groups who may
benefi t from a BCG policy.
The following groups have been assessed as falling
into the high-risk category but signifi cant debate
continues as to how extensive BCG vaccination
programs should be within them.
Aboriginals
Aboriginal people are at greater risk for developing
active TB than non-Aboriginal Australian born and
this likely refl ects socioeconomic, nutritional and
health factors. 20–22 While the number of cases of
active TB recorded is small, their rate of disease
is estimated to be about 15–20 times higher than
for the non-Aboriginal Australian born. 16–18 The rate
appears to be higher in the rural and traditional communities
compared to the urban groups.
The recommendation that at risk Aboriginal neonates
be BCG vaccinated shortly after birth is based on
the premise that in high risk populations, infants and
children have a greater potential for exposure to
an active case of tuberculosis. Infection in this age
group has a signifi cantly higher risk for producing
the severe manifestations of TB, including meningitis,
rapid dissemination and death.
Migrants
The most important factor contributing to the change
in the epidemiology of TB in Australia has been
the increased migration from countries with a high
incidence of TB. Their rates of TB remain similar to
those of their country of origin, particularly in the fi rst
5 years after arrival. 16–18
The rate of TB in children, particularly those aged
less than 5 years, is an important indicator of TB
control. The overall rates of TB for non-Indigenous
children born in Australia remain very low. While
the rates are higher in overseas-born children the
actual numbers reported are small. 16–18 Further, data
from Australian prevalence surveys indicate that the
rate of TB infection in children born in Australia of
overseas-born parents is as low as that of children
of Australian-born parents. 23–26
Hence it is now recommended that BCG vaccination
in neonates and infants of migrant parents should
be based on a careful assessment of the individual
situation.
Health care workers
Health care workers are at variable risk of being
exposed to patients with active TB. This will be
dependent on the specifi c occupation and likelihood
of contact with certain groups.
Two strategies have been advocated to control TB
in HCWs. Namely, BCG vaccination or regular tuberculin
skin testing (TST) and the use of preventive
therapy in ‘converters’. The role of BCG vaccination
in HCWs is unclear and the uncertainty has led to
divergent policies in the States and Territories and
overseas. The main issues are the lack of evidence
110 CDI Vol 30 No 1 2006